Intestinal absorption of sucrose in man: interrelation of hydrolysis and monosaccharide product absorption.

Disaccharides are hydrolyzed by their specific enzymes present in the intestinal mucosa (1-3). Although some current textbooks still state that these enzymes are secreted into the intestinal lu- men (4-7), the concentrations of monosaccharide products free in intestinal contents during disac- charide absorption in vitro (8-10) have been found insufficient to support the concept of intraluminal hydrolysis. In addition, the low disaccharidase activity of intestinal contents during the absorp- tion process in vivo (11-13) strongly suggests that the disaccharide either enters the cell before being hydrolyzed or else is hydrolyzed at the cell surface by mucosa-bound enzyme. The released monosaccharide products presumedly are then transported across the intestinal cell (8, 14, 15).